WASHINGTON -The Senate Judiciary Committee yesterday approved the nomination of Judge John Roberts Jr. to be the next chief justice of the United States, all but assuring that the 50-year-old Circuit Court judge will be confirmed by the full Senate in time to preside over the beginning of the court’s next session on October 3.

Yet a divided vote among the committee’s eight Democratic members showed what appeared to be growing confusion within Democratic ranks on how to deal with Republican judicial nominees, and raised questions about whether Democrats and their activist allies will be able to mount a unified front against the court’s other, more crucial, open seat.

Senator Clinton, the Democrat of New York who is considered a contender for her party’s nomination for president in 2008, announced late yesterday that she will vote against Judge Roberts because of a lack of certainty on his views.

“I have an obligation to my constituents to make sure that I cast my vote for chief justice of the United States for someone I am convinced will be steadfast in protecting fundamental women’s rights, civil rights, privacy rights, and who will respect the appropriate separation of powers among the three branches,” Mrs. Clinton said. “After the judiciary hearings, I believe the record on these matters has been left unclear.”

President Bush could make a decision on filling the seat of Justice O’Connor as soon as September 30, the chairman of the judiciary committee, Senator Specter, said. At least two Republican committee members used their time during yesterday’s vote to make a public plea for the president to name a conservative.

Opponents of Judge Roberts, many of whom had spent years preparing for an opening on the court, readily acknowledged yesterday that they were disappointed with Democratic committee members who voted for the nominee, including Senator Leahy, of Vermont; Senator Kohl of Wisconsin, and, perhaps most surprisingly, Senator Feingold, also of Wisconsin.

“Today was a defeat, and there is no question about that,” the president of People for the American Way, Ralph Neas, told reporters after the vote. “But as we build a progressive movement, we’re going to have ups and downs. And this was definitely a down moment.”

But several Republican senators and conservative backers of Judge Roberts argued that the focus should be on the five Democrats’ votes against the nominee rather than the three votes in his favor. They said Republicans voted as a bloc in committee to approve Justice Ginsburg as an associate justice to the court, and that Democrats had created a new standard for screening rather than simply confirming the president’s picks.

“We saw Judge Ginsburg as a competent person and we voted for her, and we did not respond to our single interest groups,” Senator Grassley, a Republican of Iowa, said. “And I’m not advocating that we do, but I guess I’m suggesting there’s a whole new ballgame out there when you have someone of the competence of Judge Roberts and you have this many people voting against him.”

At least one Democrat, Mr. Kohl, acknowledged that his vote on Judge Roberts was influenced by considerations about the next opening.

In explaining his vote in favor of the nominee, Mr. Kohl said he would not as readily have voted the way he did if Judge Roberts were up for Justice O’Connor’s seat, as he originally was, adding that he hoped the White House will keep that in mind when it considers its next nominee.

“Judge Roberts testified that his confirmation to replace Chief Justice Rehnquist will not radically shift the balance of the court,” Mr. Kohl said. “If he had been nominated, as was originally, to replace Justice O’Connor, then his confirmation would have moved the court to the right and that would have made this a much more difficult decision for me. It is my hope that the White House recognizes this concern when they choose the next nominee.”

Senate sources and activists were speculating before the vote that some Democrats might vote for the nominee as a way of gaining credibility ahead of the vote against the president’s next nominee. Such speculation has become so widespread that some have even begun talking about a so-called fall-guy nominee by the White House.

The committee’s Republican chairman, Senator Specter, of Pennsylvania, acknowledged the influence of the next nominee in speaking to reporters after the vote.

“For some time now, it has been evident that Judge Roberts was going to be confirmed,” Mr. Specter said. “Inevitably, that set the stage for the next confirmation. I think that some of the voting today was calculated to impact on the next nomination. …Voting in favor would put senators in a better position to oppose later, or a vote in opposition would put the president on notice that he better put somebody up who is acceptable to a broad spectrum of senators.”

Democrats on both sides of the nomination used similar reasoning to come to different conclusions on the nominee: Those who voted for, including Messrs. Leahy and Kohl, said they take Judge Roberts at his word that he will respect precedents such as Roe v. Wade and bring a modest temperament to the court.

Others, like Senator Schumer, of New York, and Senator Biden, of Delaware, said they could not take such a gamble without knowing the nominee’s personal views.

In explaining his vote against the nominee, Senator Durbin, of Illinois, questioned the nominee’s humanity.

Mr. Schumer, who surprised many observers when he said during the first day of the hearing that he was “pleasantly surprised” by answers Judge Roberts gave to questions about a right to privacy, said yesterday that he decided to vote against the nominee, in large part because of what he referred to as “eerie parallels” between the answers that Justice Thomas gave to questions about privacy during his own confirmation hearing in 1991 and answers Judge Roberts gave last week.

Mr. Schumer also voted against Judge Roberts two years ago when he was nominated for his current post on the Washington, D.C., Circuit.